Banding tools are well known in the art for applying tension to a band around items, such as hoses, pipes, conduit and the like, to be connected or held together. A typical band includes a length of strap, generally metal, wrapped around the item and having a buckle to connect and hold together the two ends of the strap.
It can be appreciated that the band should be fastened with sufficient tension to ensure that the band remains in place, that the items remain connected to each other and that any gas or liquid flowing through the items not leak out. However, it can also be appreciated that if too much tension is applied to the band, the items around which the band is wrapped can crack, buckle or break. It is also possible for the band itself to break, creating a significant safety hazard to the operator of the banding tool.
With respect to power-activated band tensioning tools, it is common to monitor pressure, such as air pressure. When the air pressure reaches a predetermined pressure, the application of power, via the air pressure, is discontinued. The band then has a predetermined amount of tension. Regarding manually operated band tensioning tools, U.S. Pat. No. 4,928,738 issued May 29, 1990, entitled "Tool For Tightening Cable Tie" and assigned to the same assignee as the present invention, discloses a method and apparatus for tightening band-type clamps, such as cable ties, in a desired tension. The free end of the band is inserted in the nose of the device and under a pinching roller; a handle is then squeezed toward the body of the device compressing a first spring against a bridge member to cause the bridge member to move rearward in the body of the device and compress a second spring. The pinching roller, connected to the bridge member, also moves rearward, thereby applying tension to the band. When the forces produced by the second spring and the tension in the band against the bridge member in the forward direction exceed the force applied by the first spring against the bridge member in the rearward direction, the bridge member ceases to move rearward. Further squeezing of the handle continues to compress the first spring and causes the handle to collapse against the body of the device, indicating that sufficient tension has been applied to the band. A second handle is then squeezed to cut the band. The amount of tension applied can be changed by replacing the second spring with a spring having a different compression characteristic.
Another indicator assembly is disclosed in U.S. Pat. No. 4,747,433 issued May 31, 1988 and entitled "Clamp Tightening Tool." This patent discloses a pneumatic powered device for tightening a metal band around a hose. The free end of the band is wrapped around the hose, passed through a buckle and inserted into the nose of the device. A trigger is then squeezed. A V-shaped punch pivots and rams part of the free end of the band into a V-shaped throat formed in an anvil. The punch and anvil are shifted in a direction to apply tension to the band. When the tension applied to the band reaches about 500 pounds, the end of the band breaks away from between the punch and anvil and slips out of the throat. A frosted appearance on the outer surface of the end of the band indicates that adequate tension has been applied.
However, many manual banding tools do not include an indicator. For example, one such banding tool, typical in design and operation, comprises a C-shaped frame. The frame has a nose piece having a slot for receiving the tail (or free end) of the band; the nose piece can also include a lever actuated cutting blade. Opposite the nose piece is an end piece having a bore through which a threaded rod is inserted, the respective diameters of the rod and the bore being selected to permit the rod to move freely through the opening. A clamping member is secured to the end of the rod which is within the frame (that is, between the end piece and the nose piece). The clamping member can slide along the base of the frame when the rod moves back and forth through the bore in the end piece. A handle is threaded onto the end of the rod outside the frame and is free to rotate without causing the rod to rotate.
In use, a buckle is secured to one end of a band and the band wrapped around the items to be connected. The free end of the band is passed through the buckle but is not fastened thereto. The nose of the banding tool is pressed against the buckle and the tail of the band passed through the slot in the nose of the banding tool. The tail is then secured to the clamping member, such as with a lever actuated eccentric cam.
The threaded handle is screwed onto the threaded rod until it contacts the outside of the end piece of the frame. Continued turning of the handle pulls the clamping member, with the band secured thereto, toward the end piece, thereby applying tension to the band. When sufficient tension has been applied to the band, the buckle is fastened to the band and a lever is operated to cut the tail of the band near the nose. The tail is released from the clamping member and the banding tool is ready to apply another band.
Unless the handle is turned enough, insufficient tension will be applied to the band; however, if the handle is turned too much, excess tension will be applied. Operators of the banding tool typically stop turning the handle when the handle "feels about right" or the band "looks about right". Because bands applied to different items (having different sizes, strengths, thicknesses and materials) require different amounts of tension to ensure a satisfactory connection, inexperienced operators of the banding tool may not be able to properly apply bands. Even experienced operators may not be able to consistently apply the proper tension in all applications. As previously mentioned, a fundamental concern is the risk that the band will snap and injure the operator if excess tension is applied.
Consequently, a need has arisen for an apparatus for use with a banding tool to indicate to the operator when sufficient tension has been applied to the band.